avcodec/escape124: Do not return random numbers

Fixes: out of array access
Fixes: 62164/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ESCAPE124_fuzzer-6035022714634240
Fixes: 62164/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ESCAPE124_fuzzer-6422176201572352

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/escape124.c

@@ -234,7 +234,7 @@ static int escape124_decode_frame(AVCodecContext *avctx, AVFrame *frame,
         if ((ret = av_frame_ref(frame, s->frame)) < 0)
             return ret;
 
-        return frame_size;
+        return 0;
     }
 
     for (i = 0; i < 3; i++) {
@@ -367,7 +367,7 @@ static int escape124_decode_frame(AVCodecContext *avctx, AVFrame *frame,
 
     *got_frame = 1;
 
-    return frame_size;
+    return 0;
 }